Add GitHub Actions workflow for Docker image releases

[Copilot]

Adds automated Docker image building and publishing via GitHub Actions when tags are pushed.

Implementation

• Workflow trigger: Runs on any tag push
• Multi-arch builds: Supports linux/amd64, linux/arm64, linux/arm/v7, linux/arm/v6, linux/ppc64le, linux/s390x via Docker Buildx
• Image tagging: Uses the git tag as the Docker image version (e.g., tag v1.2.0 → appwrite/requestcatcher:v1.2.0)
• Authentication: Requires DOCKERHUB_USERNAME and DOCKERHUB_TOKEN repository secrets

Usage

git tag v1.2.0
git push origin v1.2.0
# Workflow builds and pushes appwrite/requestcatcher:v1.2.0

Mirrors existing Travis CI behavior using GitHub's native infrastructure.

Original prompt

Add a github action that builds and pushes a docker image with the releases tag as the version

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